Process for oxidizing aldehydes to carboxylic acids

Abstract

Carboxylic acids having the general formula: R-COOH wherein R is selected from the group consisting of aryl, aralkyl, aralkenyl, aralkynyl, heteroaryl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, alkyl, alkenyl and alkynyl, optionally substituted by inert or non-reactive substituents under the reaction conditions, are obtained by oxidation of the corresponding aldehydes with an alkali metal or alkaline-earth metal chlorite in the presence of hydrogen peroxide and in an aqueous-organic solvent. The resulting carboxylic acids are utilizable as intermediates for preparing fine chemicals in known ways.

What is claimed is: 
     
       1. A process for oxidizing aromatic, heteroaromatic and aliphatic aldehydes having the general formula:   R-CHO     wherein R is selected from the class consisting of aryl, aralkyl, aralkenyl, aralkynyl, heteroaryl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, alkyl, alkenyl, and alkynyl, optionally substituted by substituents which are inert under the reaction conditions, to the corresponding acids of the general formula:     R-COOH     wherein R is the same as defined above, by means of an alkali metal or alkaline-earth metal chlorite, in an aqueous-organic medium, characterized in that it is conducted in the presence of hydrogen peroxide.   
     
     
       2. A process according to claim 1, characterized in that it is conducted at a temperature ranging from 0° to 100° C., and at a pH ranging from 1 to 6. 
     
     
       3. A process according to claim 1, characterized in that the aldehyde/chlorite/hydrogen peroxide molar ratios range from 1:1.1:1 to 1:5:5. 
     
     
       4. A process according to claim 1, characterized in that the chlorite is sodium chlorite or potassium chlorite. 
     
     
       5. A process according to claim 1, characterized in that the reaction medium consists of a mixture of water and of a solvent selected from the class consisting of aliphatic alcohols, cyclic ethers, acyclic ethers, and nitriles. 
     
     
       6. A process according to claim 5, characterized in that the solvent is selected from the class consisting of methanol, ethanol, iso-butanol, ter.butanol, tetrahydrofuran, and acetonitrile. 
     
     
       7. A process according to claim 1, characterized in that the aldehyde R-CHO is selected from the class consisting of cinnamaldehyde, α-methylcinnamaldehyde, benzaldehyde, 4-pyridinaldehyde, 2-thiophenaldehyde, o.nitrocinnamaldehyde, p.methoxybenzaldehyde, 3-propylacrolein, 4-nitro-2-furaldehyde, α-chlorocinnamaldehyde, p.acetamidobenzaldehyde, α-bromocinnamaldehyde, β-phenylpropargylaldehyde, and p-isobutyl-2-phenylpropionaldehyde. 
     
     
       8. A process according to claim 1, characterized in that it is conducted at a temperature ranging from 10° to 40° C., and at a pH ranging from 3 to 6. 
     
     
       9. A process according to claim 1, characterized in that the aldehyde/chlorite/hydrogen peroxide molar ratios range from 1:1.1:1 to 1:2:5.